View Single Post
Old 10th September 2010, 00:33   #7
HarryM1BYT
This is my second home
 
HarryM1BYT's Avatar
 
75 Contemporary SE Mk II 2004 Man. Sal. CDTi 135ps, FBH on red diesel, WinCE6 DD

Join Date: May 2010
Location: Garforth, W. Yorks
Posts: 16,860
Thanks: 2,107
Thanked 1,872 Times in 1,462 Posts
Default

Interesting!

My 2L 1993 petrol Granada seemed to be very thermally efficient. No matter how hard I drove it, I could never get it to fire up its cooling fans. One day, on an extremely hot day I did a fast 100 mile motorway run, then decided to check its cooling fans did actually work. I ran it straight into my garage, blanked the radiator up completely and left it ticking over. It took a further 30 minutes of this, before the first fan cut in.

Getting back to the 75's CDTi, I can understand that if it is very thermally efficient, it will simply take longer from cold to get up to temperature before the stat opens. The stat should then maintain the temperature by varying its width of opening. What I'm seeing via the OBD is the temperature rise up to the opening set point, the temperature then fall several degrees as the cool water starts to flow in, then rise back up to its stable running temperature. This is exactly what I have witnessed on other cars with a properly working stat and a temperature gauge which shows an accurate temperature.

I think radiator blinds fitted to the CDTi will have absolutely no effect. They were common in an era where radiators could freeze in cold weather and thermostates were not as efficient or accurately made as they are these days.

So the basic problem remains the CDTi's high thermal efficiency and its lack of waste energy to bring itself quickly up to temperature.
HarryM1BYT is offline   Reply With Quote